Method of removing unsaturated or aromatic hydrocarbons from gases

ABSTRACT

A GAS FILTER, PARTICULARLY ADAPTED FOR ENGINE EXHAUSTS OR FOR AIR-CONDITIONING INTAKES IN WHICH THERE IS A FIRST GAS-POROUS BAT OF FIBERS TO EFFECT MECHANICAL FILTERING OF PARTICULATE MATTER, AND A SECOND GAS-POROUS BAT OF FIBERS, STRIPS, POWDER OR THE LIKE FORMED FROM A POLYMER OF A PERHALOGENATED SULFONATED ALKENE SUCH AS PERFLUOROETHYLENE SULFONIC ACID TO EFFECT REMOVAL BY REACTION WITH UNSATURATED AND AROMAATIC HYDROCARBONS IN THE EFFLUENT FROM THE MECHANICAL FILTER.

April-16, 1974 M. J. BLOCK 3,804,943

METHOD OF REMOVING UNSATURATED OR AROMATIC HYDROCARBONS FROM GASES FiledNov. 15, 1971 INVENTOR. MYRON J BLOCK ATTORNEYS Patented Apr. 16, 19743,804,943 METHOD OF REMOVING UNSATURATED OR AROMATIC HYDROCARBONS FROMGASES Myron J. Block, 4 Clilf St., Nahant, Mass. 01908Continuation-impart of abandoned application Ser. No. 156,296, June 24,1971. This application Nov. 15, 1971, Ser. No. 198,774

Int. Cl. B01d 35/16, 53/34 US. Cl. 423-245 6 Claims ABSTRACT OF THEDISCLOSURE A gas filter, particularly adapted for engine exhausts or forair-conditioning intakes in which there is a first gas-porous hat offibers to effect mechanical filtering of particulate matter, and asecond gas-porous hat of fibers, strips, powder or the like formed froma polymer of a perhalogenated sulfonated al'kene such asperfluoroethylene sulfonic acid to effect removal by reaction withunsaturated and aromatic hydrocarbons in the eflluent from themechanical filter.

This application is a continuation-in-part of copending patentapplication Ser. No. 156,296, filed June 24, 1971, and now abandoned.

This invention is concerned with filtering of gases and vapors, and moreparticularly to filtering of hydrocarbons from the ambient atmosphere.

It is known that atmospheric pollutants include a large number ofmaterials that have a hydrocarbon structure. The term hydrocarbon asused herein is intended to include compounds that consist soley ofcarbon and hydrogen, and such compounds which are incompletelysubstituted, at least to the extent that one or more C-H moieties orparts remain in the molecule. Many of such atmospheric hydrocarbonpollutants are the pyrolytic products of partially burned gasoline, andalso residual unburned gasoline. Of the pyrolytic residues, the majorcomponents are largely vaporous unsaturated hydrocarbons and alsoaromatic hydrocarbons. The presence of these compounds in theatmosphere, particularly in large quantities as in the major cities is asource of considerable annoyance and, in fact may constitute a serioushealth hazard.

Being vaporous (which term as used herein is intended to includehydrocarbons in gaseous form as well as liquidgas aerosols in which thehydrocarbon forms either or both phases) it has hitherto been virtuallyimpossible to exclude the hydrocarbons from the atmosphere inside ofdwellings and other structures, from the intake of air compressors, orother places where the presence of these pollutants is unwanted. Onesystem in use is to scrub the intake gas with a water bath to entrap theundesired gases, but this tends to introduce unwanted moisture in manycases. Another system is to scrub the intake gas with an organic solventor oil which will absorb the hydrocarbon gases. However, even if such anoil has an extremely low vapor pressure, it nevertheless will tend tocome to equilibrium quickly with the atmosphere and will then reemit thedissolved hydrocarbons to the same extent it absorbs them. Basicchemicals and activated charcoal gas bafiles or traps are not veryselective and tend to saturate very quickly because of the presence ofCO and other acid gases in the atmosphere.

A principal object of the present invention is therefore to provide asystem for filtering or removing such vaporous unsaturated and aromatichydrocarbons from a gas stream. Another object of the present inventionis to provide such a system which employs a material which is a specificabsorber for unsaturated and aromatic hydrocarbon vapors. Yet anotherobject of the present invention is to provide a mechanically passivefilter for filtering out such hydrocarbons from a gas stream, whichfilter is simple to make, use and install.

To effect the foregoing and other objects of the present invention,there is generally provided a filter element formed of a gas-porous massof a perhalogenated alkenebased polymer containing pendant sulfonylgroups. This element can be used alone, but is preferably employed bybeing disposed behind or in the efliuent gas stream from a second filterelement. The latter is typical of the prior art and is formed of agas-porous mass which is intended simply to serve to remove, from an airstream passing therethrough, the majority of particulate matter,particularly all of the large particles, e.g. those of 100 microns ormore in diameter.

Other objects of the invention will in part be obvious and will in partappear hereinafter. The invention accordingly comprises the apparatuspossessing the construction, combination of elements and arrangement ofparts and the method comprising the several steps and order and relationthereof, all of which are exemplified in the following detaileddisclosure, and the scope of the application of which will be indicatedin the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing wherein there is shown aperspective fragmentary view, of a rfilter embodying the principles ofthe present invention.

Referring now to the drawing there will be seen a filter systemdesignated generally at 20 including a first filter element such as bat22 of fibers arranged typically in random fashion to provide a porousstructure through which a gas stream can be passed under a reasonablysmall head of pressure, as may be provided by the air intake of anair-conditioning system or the like. The fibers of bat 22 typically aremade of a relatively chemically inert material such as glass or apolymer such as ethyl cellulose, polyvinyl acetate and a host of othermaterials that can be spun or formed into the fine fibers capable offorming a bat which can function to entrap particulate matter.

Disposed adjacent bat 22 in the path of effluent gas from the latter, isa second filter element 24 formed as a gas-porous structure from apolymer of a perhalogenated sulfonated alkene-based polymer.

The latter material is a homogeneous polymer made as a fluorosulfonylderivative having a generalized formula where X is a halogen, n and pare integers, and R is a moisty selected from the groups [O(CF [-R(CFand [(CF wherein the terminal CF radical of those groups is bonded tothe OP radical connected to the sulfonyl group, m is an integer from 1to 6, R' is a perhalogenated alkyl biradical teger from 1 to 6 carbonatoms. This material is usually hydrolyzed to the sulfonic acid formdescribed as The two compounds described above (1) and (2) are highlyreactive and react with appropriate unsaturated or aromatic hydrocarbonscovalently.

Both of the compounds or derivatives are structures of a completelyhalogenated polymer that essentially has a polyperhaloalkene based typeof backbone with sulfonyl derivative (i.e. SO ended side chains andsubstantially lacks any hydrocarbon groups. The presence of O or R inthe molecule does not materially affect the reactivity or use of thematerial for purposes of the invention, nor if m' l is the reactivitymaterially affected The molecular weight of the material is notparticularly important inasmuch as the desired reactivity with theparticular hydrocarbon gases is due to the presence of the fiuorsulfonylgroups. In this regard, the number of sulfonyl groups can be varied ascan the number of CF groups. The halogen substitutions on the backbonecan be either fluorine, chlorine or other halogens in mixed proportions,but the backbone should be perhalogenated to insure that substantiallyno hydrogens remain bonded to the molecule. Typically then, themolecular backbone if perfluorinated, is similar to thepolytetra-fluoroethylene type of backbone; and if partially chlorinatedthen similar to the backbone of Kel-F (a trademark of the 3M Company)i.e. a chloro 3-fiuoroethylene polymer with fiuorsulfonyl side chains.Thus, the polymeric material can vary fairly widely in molecular weight,retention capacity, and electrical and mechanical characteristics.However, where the polymer is preferably substantially completelyhalogenated and possesses fiuorsulfonyl side chains, it will provide theproperties required for purposes of the invention. Generally, it ispreferred to use polymers of the lowest equivalent weight provided thatthe weight is not so low that the polymer becomes unstable at roomtemperature. This serves to increase the ratio of sulfonyl groups tocarbon atoms and thus increase the retention capacity.

Polymers of this type are described more fully in US. Pat. No.3,282,875, and an exemplary film thereof is available from E. I. du Pontde Nemours & Co., Inc., Wilmington, Del., under the trade designation XRPerfluor-Sulfonic Acid Membranes.

As a characteristic of this type of polymeric structure (herein calledperhaloalkene sulfonyl polymers), hydrocarbon vapors, both unsaturatesand aromatics, tend to diflFuse readily into the polymer. The polymericmaterial has an upper use temperature, typically around 225 C. for theabove-identified film depending on the equivalent weight of the membrane(usually up to about 1300 equivalent weight range), the environmentemployed and the desired service life.

This perhaloalkene sulfonyl material, such as polytetrafiuorethylenesulfonic acid, will readily act to scrub a gas stream passingtherethrough, to remove vapors of certain hydrocarbons which contain oneor more multiple carbon-to-carbon bond, and one or more CH, moiety(where t is an integer from 1 to 3). These latter hydrocarbons may betypified generally as the aromatic hydrocarbons and the unsaturatedhydrocarbons. Typically, the perfluorsulfonic acid type material willreact with the vapors of such aromatics as benzene, xylene, anthracene,naphthalene, carbazole and even mixtures such as ligroin or petroleumether. The membrane will also react with the vapors of unsaturates suchas the alkenes, conjugated dienes, alkynes and the like.

The reaction with these particular hydrocarbon vapors is believed due toa sulfonation reaction in which the hydrocarbon vapor molecule R" isattached at the fiuorsulfonyl (-CF -SO sites to form a sulfonederivative wherein the terminal group then becomes (CF -SO R").

The requisite polymer is in comminuted form. For example, in oneembodiment the polymer is formed of a plurality of thin sheets orstrips, e.g. l or 2 mils thick in substantially parallel relation,spaced from one another to permit passage of gas between them.Alternatively, element 24 can be formed of a porous mass of loose powderpacked in a container, or a porous sheet of lightly sintered powder, oras a mass of fibers formed as by shredding or slitting sheet material.

The term comminuted is also intended to cover other structures as well,in which similar interstitial spaces exist between small bodies ofpolymer to permit relatively free passage of an air stream over thepolymer surface and through one body, and also provides a relativelyhigh surface-to-volume ratio. While it is appreciated that the polymeritself is quite gas permeable, it is desirable to provide a gas-porousstructure which will not provide excessive mechanical impedance to airflow and will tend to insure that the desired reactions will occur evenduring very short transit time for gas passing through the filter.

As is shown in the drawing, the filter system is formed so that theperhaloalkene sulfonyl polymer filter element 24 is downstream from bat22 with respect to the expected direction of air flow as shown by thearrow. Bat 22 serves to remove particulate irritants from the air flow,prefiltering reduces the probability that element 24 will becomeclogged. One can expect that bat 22 will be considerably less expensiveand thus more readily disposable than element 24.

Bats 22 and filter element 24 are typically held in the desiredrelationship to one another by frame 26, which can be quiteconventional. The frame can be designed to fit whatever device orstructure with which the filter is to be used. For example, the framecan be a large rectangular form designed to fit in air-conditioningunits or can be a small circular shape intended to fit into exhaustsfrom internal combustion engines. In the latter case, the filterfunction is to directly remedy the pollution effect of the engineexhaust rather than to attack the problem after the ambient air has beenpolluted.

The amount of a particular hydrocarbon that can be removed depends uponthe equivalent weights of the polymer forming filter element 24 and themolecular weight of the hydrocarbon. By way of example, a filter havinga kilogram of the requisite polymeric materail should scrub atsaturation about 12,000,000 cubic feet of air containing an equivalentin benzene of 0.5 p.p.m.

Since certain changes may be made in the above apparatus and methodwithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted in an illustrative and notin a limiting sense.

What is claimed is:

1. Method of filtering a gas stream containing a quantity of unsaturatedor aromatic hydrocarbons in vaporous form comprising the step ofcontacting said gas stream with a surface of a completely halogenatedalkenebased polymer having pendant active fluorsulfonyl groups, toinduce chemical reaction between said polymer and the vapors of saidunsaturated and aromatic hydrocarbons.

2. Method as defined in claim 1 including the step of prefiltering saidgas stream to reduce the amount of particulate matter therein prior topassage over said polymer surface.

3. A method as defined in claim 1 wherein said polymer has thegeneralized formula where X is a halogen, n and p are integers, and R isa 5 moiety selected from the group consisting of the radicals z)m], [R(2)m*] and wherein the terminal --CF portion of said radicals is bondedto the CF portion connected to the fiuorosulfnyl group, m is an integer,and R is a perhalogenated alkyl biradical having from 1 to 6 carbonatoms.

4. A method as defined in claim 3 wherein X is fluorine.

5. A method as defined in claim 1 wherein said polymer has thegeneralized formula where X is a halogen, n and p are integers, and R isa moiety selected from the group consisting of the radicals z)m-], [--R(2)m-] and wherein the terminal --CF portion of said radicals is bondedto the CF portion connected to the fluorsulfonyl group, m is an integerand R is a perhalogenated alkyl biradical having from one to six carbonatoms.

6. A method as defined in claim 5 wherein X is fluorine.

References Cited UNITED STATES PATENTS 2,430,861 11/1947 Carpenter eta1. 423--230 2,664,340 12/1953 Houdry 423213 3,019,854 2/1962 OBryant55-Dig. 16 3,282,875 11/1966 Connolly et a1. 260-87.5 R

EARL C. THOMAS, Primary Examiner US. Cl. X.R.

55Dig. 16; 423212 PO-WSO I UN TED-@STATES PATENT OFFICE I w I, o v I *CERTIFICAT'E OF CORRECTION f I V 3,804,943 y April l6, 1974 P ac anteNo-. Daz d I In\ rent :or (s) MXRON J BLOCK I It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby correeted as shown/below:

;[N THE SPECIFICATION:

Column 2, line 55, delete SO F and substitute therefor -v---SO F IN THECLAIMS:

Column. line 70 the formulashould be corrected as follows:

" P0405) UNITED STATES PATENT OFFIU (5/69) I C TE OF CORRECTION Parent;No 0 r 9 3 a April 16 1.974

Inventor(s) MYRON J. BLOCK PAGE 2..

It is eertified th'at error appears in the above-identified patent andthat said Letters Patent are hereby correered as shown below:

r'q Y K o...

Column 5-, line' 15, the formula should be corredted as follows:

(SEAL) Attesc:

MCCOYM'. GIBSON JR. 7 i C. MARSHALL DANN Arresting Officer vCommissioner of Patents

